1. Technical Field
The present invention relates to information processing systems that operate with a low power consumption, and more particularly to a portable information processing system such as a notebook computer.
2. Description of the Related Art
As a result of the recent technological innovation, small-size and light-weight portable computers have become common. When such portable computers are used outdoors, electric power is supplied to them with batteries. However batteries mounted on portable computers are restricted to small-size batteries. Thus the length of time that personal computers can be operated during a single charge of the batteries is short. Consequently, various kinds of devices are provided for reducing the consumption of power in many portable computers.
A suspend/resume function is one such device. When the suspend/resume function operates, the computer enters into a suspend mode in response to such a situation as one in which the activity of I/O device is not detected for a certain time. In the suspend mode all tasks are suspended, and the main memory saves data required later for resuming the tasks. In the suspend mode, the main memory and the video memory (VRAM) are powered on, but CPU or the like are powered off. However, portable computers have a drawback in that the power of batteries are consumed when the suspend mode continues very long with only the support of the suspend/resume function resulting in the contents of the memory and the VRAM being erased.
Accordingly, portable computers, which are supported with hibernation mode, such as the LTE Lite/25 manufactured by Compaq Company (Compaq and LTE are registered trademarks of Compaq Computer Corporation), have been proposed and marketed. When hibernation mode is enabled, the computer enters a low battery state. Otherwise, when the suspend mode continues for a certain time, the computer enters hibernation mode after saving all the data required for resuming the task later onto the hard disk. In hibernation mode, the whole system, including the memory and the VRAM, is powered off. When a user powers on the system later, the data stored in the hard disk is restored in the memory and the VRAM and the task which had been suspended are automatically resumed. The series of operation accompanying power-on is also referred to as wake-up.
In recent years detachable hard disk devices have come to be installed on computers. However, no art is known that enables carrying a detachable hard disk device in which a task is frozen and installing such a device in a different system in which the task is thawed (resumed).
A prior solution is a technique in which the part for holding the necessary information for resumption constitutes a cassette construction detachable from the main body of the computer with the content held as it is. However, in this technique, the main memory itself is set so as to be non-volatile, and can be detached from the main body of the personal computer. Consequently, the above conventional art does not suggest means for solving the problem which is intended in the present invention.
Accordingly, what is needed is a way of storing information to an external storage device detachable from the volatile main memory and for restoring the information.